WASHINGTON — The average rate on the U.S. 30-year fixed mortgage last week dipped closer to the lowest on record, a trend that is making home buying more affordable and also enabling more Americans to refinance their loans.

Mortgage buyer Freddie Mac says the average rate on a 30-year loan declined to 3.35 percent from 3.37 percent last week. That’s not far from the 3.31 percent rate of about a month ago, the lowest on records dating to 1971.

The average on the 15-year fixed mortgage was unchanged at 2.65 percent. The record low is 2.63 percent.

The 30-year fixed mortgage rate averaged 3.66 percent this year, Freddie Mac said, the lowest annual average in 65 years.

Frank Nothaft, chief economist at Freddie Mac, said the average 30-year rate has fallen 0.6 percentage points this year. That would save a homeowner about $98,000 in interest payments over the life of a $200,000 loan, he said.

The Federal Reserve is purchasing about $85 billion each month in Treasury bonds and mortgage-backed securities in an effort to push down long-term interest rates.

In a separate report, the Commerce Department said that sales of new homes jumped 4.4 percent in November to a seasonally adjusted annual rate of 377,000. That is the fastest pace in more than two and a half years and the latest sign the housing recovery is sustainable.

Low mortgage rates and steady hiring gains have encouraged more people to buy homes. Home owners may also put their homes up for sale if they feel confident they can sell at a good price.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country on Monday through Wednesday of each week. The average doesn’t include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for 30-year loans was 0.7 point, unchanged from last week. The fee for 15-year loans was also unchanged at 0.7 point.

The average rate on a five-year adjustable-rate mortgage ticked down to 2.70 percent from 2.71 percent last week. The fee was also unchanged at 0.7 point.

The average rate on a one-year adjustable-rate mortgage rose to 2.56 percent from 2.52 percent. The fee for one-year adjustable-rate loans rose to 0.5 point from 0.4 point.